Catching a supernova just before it happens

By grigoris | Filed in Astronomy

Victor Buso is a really very lucky man! On September 20, 2016 we wanted to test his new camera mounted on a 40-cm Newtonian telescope. He pointed to the spiral galaxy NGC 613 because it was at that time located near the zenith. He took a series of 20s exposures spanning approximately an hour and a half. During the first part (about 40 exposures) there was no sign of anything unusual. After a break of 45 min though the exposures that he took revealed the rise of a supernova (SN 2016gkg). He is the first person to ever achieve that, ie. to capture the rise of a supernova just before its maximum light!

These observations are an unprecedented set of data for supernova physics. According to the recent paper by Bersten et al (incl. Buso) 2018 the data shows the clear presence of the shock breakout phase in the optical, i.e. the phase associated with the propagation of the radiation shock inside the star and its dissolution at the surface (Waxman & Katz 2016). This lasts seconds to a fraction of an hour typically, unless there is enough circumstellar mater ejected from the progenitor star before the supernova explosion then this phase may extend to days. The phase produces bright X-ray/UV flash but its optical manifestation has not been observed. So these observations show that the optical light curve is characterized by an extremely rapid brightening at relatively low luminosity.

What I find very critical in this work is actually how quick-witted Buso was. He is an amateur astronomer that didn’t just take the images. Instead he properly reduced them and he noticed the difference. The next important step was to communicate this to the appropriate channels that allowed for follow-up observations to be obtained in in less than a day later (including Swift X-ray, UV and optical telescopes, see Bersten et al 2018 for a list).

References
Bersten et al, 2018, Nature, 554, 497 (NASA/ADS link)
Waxman & Katz, 2016, arXiv:1607.01293 (arXiv link)

Skinakas return!

By grigoris | Filed in Astronomy

Yesterday was the first night that I found myself at Skinakas Observatory. Even though some years have passed, there are really minor changes. The mountain welcomed us with great weather (scarce clouds, humidity close to 50%, and almost no wind at all!), while the seeing proved to be really good (~1″).

The 1.3m Skinakas telescope.

Mixing a transient object with … Mars!

By grigoris | Filed in Astronomy

In the Astronomer’s Telegram #11448 [1] it is announced that a very bright (almost 1st magnitude) transient object is found between the Lagoon and the Trifid nebulae. No other object has been found in the region and the source itself was not visible some days earlier.

Within less than an hour later a second follow up telegram (#11449) informs the community that the transient object is … Mars !

It goes without saying that errors are for humans. But this one shows that every astronomer has to have a basic grasp of the night sky at least.

[1] http://www.astronomerstelegram.org/?read=11448
[2] http://www.astronomerstelegram.org/?read=11449

Seminar talk at NOA

By grigoris | Filed in Astronomy

As I am waiting my flight to Heraklion, I thought that I should post the talk that I gave earlier today at the National Observatory of Athens, Greece:

“B[e] Supergiants: a missing part from the massive star puzzle?”

Abstract:
Massive stars affect strongly the insterstellar medium through their intense stellar winds and their rich chemically processed material as they evolve. This interaction becomes substantial in short-lived transition phases of massive stars (e.g. B[e] Supergiants, Luminous Blue Variables, Yellow Hypergiants) in which mass-loss is more enhanced and usually eruptive. Consequently, a complex environment, combining atomic, molecular and dust regions is formed around these stars. In particular, the circumstellar environment of B[e] Supergiants is not well understood. Moreover, their possible link to other phases has not been fully uncovered yet, which is crucial given the importance of massive stars for Stellar Astrophysics and their influence on their host galaxies. Starting from an observational point of view, I will provide an overview of the B[e] Supergiant population and discuss the latest results.

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Proposal brainstorming …

By grigoris | Filed in Astronomy

From our previous meeting.

Putting ideas on the chalkboard (Image © Paul Sell, CC BY-SA-ND).

During the last few days I have struggled a bit with the wavelength calibration of some long-slit spectra. When using the identify task of IRAF I found that I could select (“m”ark) only some of the lines, without any clear indication why the rest were not recognized (some were indeed stronger but others were equal or weaker). The actual error that kept popping out was “Center not found: check cursor position”. Although I went on to investigate all parameters (even the aidpars !) the one thing that solved the problem was finally to increase a bit the full-width of the features to be identified (fwidth), from the default value of 4.0 to 10 pixels. Apparently some of the lines seems too wide to be determined as real features by the task.

New position at FORTH and UoC

By grigoris | Filed in Astronomy

Since October 2017 I have been affiliated with the Department of Physics at the University of Crete, but last week I started working officially as a post-doc with Andreas Zezas. The position is directly affiliated with the Foundation for Research and Technology – Hellas (FORTH), and in particular with the Institute of Electronic Structure and Lasers (IESL).

A new Institute for Astronomy in Crete

By grigoris | Filed in Astronomy

Finally after many years of delays and unfortunate events a new institute focusing solely in Astronomy is founded as part of the Foundation for Research and Technology – Hellas (FORTH). This is the successful outcome of a continuous effort by the very active astronomy group at the University of Crete. Congratulations to the group and we anticipate the future achievements!

Our recent work on the identification of star clusters in the Small Magellanic Cloud (SMC), following the initial work on the Large Magellanic Cloud, was selected by Nature as a research highlight [1]. The distribution of the star clusters and their ages can reveal us how the two galaxies interact and when. It seems that the majority of the stars were born after this interaction.

[1] https://www.nature.com/articles/d41586-018-01598-x, Nature site, accessed on Feb. 5, 2018.

Jobs in Astronomy by Peblo

By grigoris | Filed in Astronomy

How easy is it really to find a job in Astronomy?

To find out check the following illustration by by Peblo, describing job applications:

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